Recently, rechargeable electric storage devices such as battery cells, e.g., lithium ion cells and nickel hydrogen cells, and capacitors, e.g., electric double layer capacitors, are employed as a power source for vehicles, e.g., cars and motorcycles, or various appliances, e.g., mobile terminals and laptop computers. Such an electric storage device is disclosed, for example, in JP 2007-265666 A.
JP 2007-265666 A discloses a non-aqueous electrolyte secondary cell using a separator in which clogging is less likely to occur even if a charge-discharge cycle is repeated. JP 2007-265666 A discloses a non-aqueous electrolyte secondary cell in which the compression resistance rate per unit film thickness is not more than 100 seconds/μm, when the separator has a compressibility of 20%, for the purpose of providing a non-aqueous electrolyte secondary cell with excellent load characteristics and cycle characteristics. JP 2007-265666 A discloses that the compressibility of the separator is defined as: (film thickness before compression of separator—film thickness after compression of separator)/(film thickness before compression of separator)×100, and the compression resistance rate of the separator is defined as: (air resistance after compression of separator—air resistance before compression of separator)/(film thickness before compression of separator—film thickness after compression of separator)×100, in which the air resistance is measured to in accordance with a measurement method prescribed in JIS P8117.
Since the non-aqueous electrolyte secondary cell of JP 2007-265666 A uses a separator having an excellent compression resistance, the air resistance of the separator is less likely to increase even if the separator is compressed by swelling of the positive plate and the negative plate with the evolution of the charge-discharge cycle, and therefore clogging is less likely to occur in the separator. Accordingly, the ion conductance of the separator is hard to decrease in the non-aqueous electrolyte secondary cell of JP 2007-265666 A. Thus, the above-mentioned purpose is achieved.
In this way, JP 2007-265666 A discloses a non-aqueous electrolyte secondary cell for achieving excellent cycle characteristics after repetition of the charge-discharge cycle.